Oral phage therapy with microencapsulated phage A221 against Escherichia coli infections in weaned piglets

Escherichia coli (E. coli) is a common pathogen that often causes diarrhea in piglets. Since bacteria are becoming more and more resistant to antibiotics, phages have become a promising alternative therapy. However, the therapy of oral phage often fails to achieve the desired effect. A novel phage named A221 was isolated by using E. coli GXXW-1103 as host strain, characterized by electron microscopy, genomic sequencing and analyzed by measuring lysis ability in vitro.

Phage A221 was identified as a member of Ackermannviridae, Aglimvirinae, Agtrevirus with 153297 bp genome and effectively inhibited bacterial growth in vitro for 16 h. This study was conducted to evaluate the therapeutic effect of oral microencapsulated phage A221 on E. coli GXXW-1103 infections in weaned piglets. The protective effect of phage was evaluated by body weight analysis, bacterial load and histopathological changes. The results showed that with the treatment of phage A221, the body weight of piglets increased, the percentage of Enterobacteriaceae in duodenum decreased to 0.64%, the lesions in cecum and duodenum were alleviated, and the bacterial load in the jejunal lymph nodes, cecum and spleen were also significantly different with infected group (P < 0.001).

The results showed that phage A221 significantly increased the daily weight gain of piglets, reduced the bacterial load of tissues and the intestinal lesions, achieved the same therapeutic effect as antibiotic Florfenicol. Taken together, oral microencapsulated phage A221 has a good therapeutic effect on bacterial diarrhea of weaned piglets, which provides guidance for the clinical application of phage therapy in the future.